gmorita

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Design & Development Engineering

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gmorita

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  • 01.11.2018
  • BRAVE new ITAR/EAR-free space-grade FPGAs
  • The 12 transistor SRAM cell is not dependent on the W/L of the transistors and has high immunity to the variability of the transistor parameters. Because ofthe ratio-less nature of this SRAM cell it is free from Static Noise Margin (SNM) considerations. This makes the SRAM cell particulary immune to degradation due to total dose and also hardens the SRAM to SEU.
  • 05.07.2015
  • Effect of external components tolerance on CMRR
  • You also need to consider any phase delay between the inverting and non-inverting inputs. Since there is always some parasitic capacitance, the CMRR may become severely degraded at relatively low frequencies, especially if high value resistors are used. Worse yet, I have seen designers place RC filters in the signal path of both inputs in an attempt to eliminate out of band noise. Most capacitors have a tolerance of 10% or at best 5%. This mismatch will cause a a phase difference of several degrees well over a decade below the RC corner frequency. This phase difference will further degrade the CMRR. While it is relatively easy to get 0.1% or even tighter tolerance resistors, 1% capacitors rare, expensive, and bulky. It's been my experience that the CMRR of a differential amplifier is controlled by the quality of the passive components around the IC opamp.
  • 03.02.2015
  • Voltage indicator transitions between colours
  • You can also replace the zener with a low current shunt voltage reference like the LT1389 for a sharper knee and resize R2 to reduce the total current in the zener leg.
  • 04.04.2013
  • The battery question I really dread
  • The question I really hate is "How long is it going to take to fix it?" when I haven't even started to troubleshoot the problem...
  • 03.14.2013
  • Nothing new about energy harvesting
  • Back during the Cold War, the Russians had a set up to power radios from with a kerosene lamp. It used a ring of what were essentially thermocouples set on top of the lamp. the hot junctions were set above the flame and the cold junctions were cooled by the ambient air. Apparently they were able to generate several watts with is simple device.
  • 02.27.2013
  • Can engineers effectively design at home?
  • There are times when working from home is very much dependent on the type of work you do. For instance, as an applications engineer, I could work on product specifications, layout circuit boards, or write application notes in the comfort of my home and avoid the hour plus commute. I work at a remote site for a global company and we have team meetings with other remote sites in Asia and Europe. These usually happen before 8am or after 5pm several days a week. Many times I will call into the meeting from home, especially if it's early in the morning. However, there are times when I have to be in the office. Evaluating a new hardware design or a customer issue requires access to equipment and other tools. Since I don't have a temperature chamber or $300K worth of specialized test equipment in my garage, the only option is to work in the office. Also, having someone else around when troubleshooting can be helpful. A couple people here have dismissed the value of office talk. I find that having other engineer's around to brainstorm or help solve a problem is invaluable. I've never met an engineer who didn't benefit from having peers around to bounce ideas off of.
  • 09.05.2012
  • How well does Gorilla Glass work?
  • Most people equate hardness with toughness. As any mechanical/materials science engineer will tell you they are two unrelated properties. The most commonly used example is diamond. Now, diamond is the hardest naturally occurring material and it will resist scratching from anything softer. However, the same molecular structure that imparts this incredible harness, also make diamond relatively brittle. Diamonds have been known to shatter if dropped a few feet onto a hard surface. If you don't believe it, just try smashing your wife's (or your) wedding ring with a hammer and see what happens to the diamond. A counter example is jade. The hardness of jade is somewhat lower that quartz (sand) but since it is made of a mesh of billions of nano fibers, it is tougher than steel. Jade "battle axes" have been found in archeological sites in South America. There is evidence that their use was not only ceremonial. The chemical process used to make Gorilla Glass does improve both the toughness and hardness to some degree. Just don't expect Gorilla Glass to be indestructable. It should be no surprise that Gorilla Glass can be scratched or shattered in normal use, it is only glass after all.
  • 11.15.2011
  • Chevy Volt fires cause concern
  • Bill, I disagree with your statement that a ruptured fuel line poses a greater fire hazard. Lithium battery fires a notoriously difficult to extinguish once they have started. Water or foam are the WORST things to pour on this type of fire because the lithium will tear the oxygen right out of the water molecule. Then you've got lithium AND hydrogen burning. If the lithium battery is a cobalt or manganese oxide type, then it has the fuel (lithium) and oxidizer (metal oxide) in close proximity to each other. Cobalt oxide based cathodes are especially problematic since the cobalt oxide decomposes above 175C releasing oxygen. I believe the Chevy Volt batteries use cathodes based on a manganese oxide chemistry and are therefore more stable.
  • 06.22.2011
  • Photo gallery: Engineering's messiest desks
  • My workbench is usually fairly messy while I am actively working on project. I have a fairly standard suite of instruments that I have set up on my bench. However, I almost always tear down the rest of the test set up and re-build a new test set up from scratch when I transition to a new board/project. This means putting (horrors!)EVERYTHING including test leads and probes away. I do this mostly to make sure that I have everything hooked up properly. I have been bit too many times thinking that the set up was correct when in fact, some remnant of the previous project was still connected and screwing up my measurements.